Electric conductive ceramic guide

ABSTRACT

An electro-conductive ceramic guide made by the use of a mixture of a metallic titanium and metallic titanium dioxide prepared at a mol ratio of 1 : 0.06 - 1.22, molding this mixture into an element of desired shape, and sintering the shaped element at 1,200* - 1,450* C in vacuum or in an inert atmosphere to cause the crystal particles of the element to have a face-centered cubic crystal structure. The resulting element is mounted at a site where it is brought into a running tape or like article. This guide is of a very small friction coefficient and imparts a stable low tension to the running tape, and has a high electroconductivity thereby being capable of removing static charge of the tape and is highly suitable for guiding video tapes and computer tapes.

United States Patent Matsumoto ELECTRIC CONDUCTIVE CERAMIC GUIDE [75]Inventor: Ryoso Matsumoto, Kyoto, Japan [73] Assignee: Oda Gosen KogyoKabushiki Kaisha, Komatsu-shi, Ishikawa-ken, Japan 221 Filed: Jan. 8,1973 [21] Appl. No.: 321,979

[30] Foreign Application Priority Data July 7, 1972 Japan 47-67569 [52]US. Cl. 226/196 [51] Int. Cl B65h 23/04 [58] Field of Search 226/196,197, 198, 199; 242/76 56] References Cited UNITED STATES PATENTS.

3.143170 8/1964 Cohen 226/196 3.087.665 4/1963 Thomas 226/198 X2,862,715 12/1958 McDonald 226/196 Primary ExaminerAllen N. KnowlesAssistant Examiner-Gene A. Church Attorney, Agent, or Firm-Cushman,Darby & Cushman [57] ABSTRACT An electro-conductive ceramic guide madeby the use of a mixture of a metallic titanium and metallic titaniumdioxide prepared at a mo] ratio of 1 0.06 1.22, molding this mixtureinto an element of desired shape, and sintering the shaped element at1,200 1,450 C in vacuum or in an inert atmosphere to cause the crystalparticles of the element to have a facecentered cubic crystal structure.The resulting element is mounted at a site where it is brought into arunning tape or like article. This guide is of a very small frictioncoefficient and imparts a stable low tension to the running tape, andhas a high electro-conductivity thereby being capable of removing staticcharge of the tape and is highly suitable for guiding video tapes andcomputer tapes.

3 Claims, 5 Drawing Figures PAIENIEBMARZS 1914 3.799.422

WU 1 [1F 2 FIG. 3

ELECTRIC CONDUCTIVE CERAMIC GUIDE BACKGROUND OF THE INVENTION tapes inelectro-magnetic tape recorders, videorecorders and electroniccomputers. In these metal guides, it has been the practice to give themetal guide an appropriate smoothness to its surface by applying hardchrome-plating onto the surface of the metal guide in order to reducethe friction resistance produced at the time the metal guide is broughtinto contact with the running tape and in order to impart a stabletension to the running tape.

However, such a conventional metal guide tends to produce uneven surfacewear due to the friction occurring during the contact between the metalguide and the running tape during use, resulting in changes in thefriction coefficient, and this in turn gives rise to uneven tension inthe magnetic tape. As a result, there are produced fluctations in thereproduction signal frequency due to the fluctations in the speed of therunning tape occurring at the time of recording and reproduction, or inother words there develops the so-called wowflutter phenomenon. Thus,the conventional metal guides had the drawback that it was difficult toeffect recording and reproduction of sounds and images of highly goodquality.

SUMMARY OF THE INVENTION It is, therefore, the primary object of thepresent invention to eliminate the aforesaid drawbacks andinconveniences of the prior art and to provide an improved guide whichinsures that always a stable tension is applied to the running tape orlike article so that it is possible to obtain good recording andreproducing signals during the use of the guide fonan extended period oftime.

Another object of the present invention is to provide anelectro-conductive ceramic guide which produces very little frictionalresistance when it is in contact with a running tape or like article.

Still another object of the present invention is to provide anelectro-conductive ceramic guide which does not develop uneven surfacewear during use, i.e., during its contact with a running tape or likearticle.

Yet another object of the present invention is to provide a method ofmanufacturing the guide of the type described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal sectionalview of the guide representing the first embodiment of the presentinventron.

FIG. 2 is a longitudinal sectional view of the guide representing thesecond embodiment of the present invention.

FIG. 3 is a chart showing the relationship between the frictioncoefficient and the load.

FIG. 4 is a chart showing the relationship between the frictioncoefficient and the temperature.

FIG. 5 is a chart showing the relationship between the frictioncoefficient and the relative humidity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS After an extensiveresearch to obtain recording and reproducing signals of good qualitycontinuously for a lengthy period of time by the constant application ofa stable tension to a running tape, it was found that anelectroconductive ceramic guide consisting of a shaped sintered elementof titanium monoxide whose crystal structure is that of face-centeredcubic was outstandingly superior as a guide for magnetic tapes. Thisdiscovery has led to the present invention.

Description will hereunder be made on some of the embodiments of thepresent invention by referring to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of the first embodiment of theguide of the present invention. In FIG. 1, reference numeral 1represents the body of a guide element A having a hollow cylindricalconfiguration. 2 represents a metal screw. 3 represents a bottom plateof the guide element. 4 represents a metal base nut. Both the body 1 ofthe guide element and the bottom plate 3 are formed integrally with asintered shaped titanium monoxide having crystal particle consisting offace-centered cubic crystal structure. The metal screw 2 passes throughthe hollow portion of body 1 and the bottom plate 3 and threadablypasses through the base nut 4 and engages the support 5 to which theelement is to be attached.

FIG. 2 is a longitudinal section view of the second embodiment of theguide of the present invention. In FIG. 2, reference numeral 6represents the body of a guide element B of a hollow tapered cylindricalconfiguration. 7 represents 'a threaded rod having male threadedportions formed at the opposite ends. 8 represents a top plate ofelement B. 9 represents a bottom of the plate of the element B. Theseplates are integral with the body 6. 10 represents a metal top-nut. llrepresents a metal base-nut. The body of the guide ele' ment B, the topplate 8 and the bottom plate 9 of the guide element B are each formedwith a shaped sintered titanium monoxide having crystal particlesconsisting of face-centered cubic crystal structure. Also, the threadedrod 7 passes through the hollow portions of the bottom plate 9, the body6 and the top plate 8 and threadably engages the top-nut 10 at the upperend and threadably engages the base-nut 11 at the lower end, andtherefrom threadably engages the support 12 to which the element is tobe attached.

Next, description will be made on an example of the method ofmanufacturing the guide of the present invention.

Metallic titanium powder and metallic titanium oxide which are thestarting materials are mixed together at a mol ratio of l 1 and theresulting mixture is shaped into a desired configuration by compressionmolding. This shaped mixture is sintered in an inert gas (such as argon)at 1,300 C. As a result, there is obtained a sintered, very hard andfirm element including the bottom and/or the top plates. Moreover, thissintered element consists of a sintered and molded titanium monoxidewhose crystal particles are of face-centered cubic crystal structure.Accordingly, it is only necessary to make the body I, the bottom plate 3of the guide element A of the first embodiment, the body 6, the topplate 8 and the bottom plate 9 of the guide element B of the secondembodiment in accordance with the example of the method stated above. Itshould be noted that it is never harmful to add about 1 percent ofpowder of clay or the like to the mixed starting materials in order toelevate the effect of sintering.

The guide element A or B of the first or the second embodiment which isobtained in this way is of portions serving as a guide which are broughtinto contact with a running tape-like article, so that this guide A or Bis capable of continuously imparting a very stable tension to thetape-like article, particularly a magnetic tape.

According to the experiment conducted by the inventor, theelectro-conductive ceramic guides each consisting of a sintered TiO andbeing a shaped sintered titanium monoxide element whose crystalparticles had a face-centered cubic crystal structure, i.e., theelectroconductive ceramic guides consisting of sintered materials havingTiO phase, when used with, for example, a polyester-based magnetic tape,exhibited a friction coefficient much smaller than did conventionalmetal guides as will be discussed later. Not only that, but also theceramic guides of the present invention shown hardly any fluctuation inthe tension of the running tape throughout the continued use for anextended period of time. Also, the electro-conductive ceramic guides ofthe present invention were incorporated in high-grade tape recorders,and the amount of wowflutter was determined according to the test tapereproducing method. The result was that the value of the determinedamount was 0.02 rms or less at the tape speed of 19 cm/s. This value wasabout one-fifth of the value obtained by the use of a conventional metalguide. Thus, it was possible to improve the quality of tape recorders.

The reasons why the electro-conductive ceramic guide consisting of amolded sintered piece of TiO phase has a small friction coefficient andis stable against the change in ambient temperature and ambient relativehumidity as stated above are considered to be explained as follows. Thesintered piece of TiO phase has a crystal structure which isface-centered cubic and in addition this piece is an oxide of titanium.Therefore it has a large yield point pressure. Besides, in the crystalparticles which constitute the sintered piece of TiO phase, there arepresent regularly disposed oxygen atoms and lattice defect of titanium.Thus, this guide has a reduced area in which it contacts the runningtape or like article. And along with this, the guide has a largeelectro-conductivity. Accordingly, the guide does not develop anyphenomenon of adhering to the tape which would be caused if the latterstores static charge. Moreover, the sintered piece of TiO phase isrelatively irregular in the dispositional arrangement of the crystalparticles and the non-crystal regions, and its crystal particles whichare needle-like particles ofa size of the order of -20 microns arescattered. Thus, this sintered piece of TiO phase essentially has thecharacteristic of being small in friction resistance.

In FIG. 3 is shown the result of determination of changes in thefriction coefficient p. when the guides of the present invention and theprior art are brought into contact with the base face of a running tapewhile changing the value of the load L of the running tape under theconditions that the ambient temperature is 25 C and the ambient relativehumidity is 73 percent. In the chart of FIG. 3, the vertical axisrepresents the friction coefficient u, and the horizontal axisrepresents the load L (gram) of the running tape. The Curve [3 indicatesthe change caused by the use of the electroconductive ceramic guides Aand B of the present invention. The Curve 14 indicates the change causedby the use of conventional metal guides. As will be understood f'rom thechart of FIG. 3, the friction coefficient 11. due to the use of theceramic guide of the present invention is of the order of 0.2 Thefriction coefficient t has a negative characteristic that the valuedecreases somewhat with an increase in the load L of the running tape.Nevertheless, the friction coefficient may be termed roughly as constantand has a low friction coefficient characteristic. Therefore, the guideobtained according to the present invention is suitable particularlywhen it is provided in a tapered configuration B as shown in FIG. 2, ascompared with a conventional metal guide which has problems when it isprovided in a tapered form.

In FIG. 4 is shown the result of the test on the changes in the frictioncoefficient of the guides of the present invention and the prior artrelative to the change in the temperature at the tape speed of 19 cm/s.In FIG. 4, the vertical axis represents friction coefficient p. and thehorizontal axis represents temperature I C). The Curve 15 indicates thechange due to the use of the electro-conductive ceramic guides accordingto the present invention. The Curve 16 indicates the change due to theuse of the conventional metal guides. As will be understood from FIG. 4,according to the use of the guides of the present invention, a low andgenerally stable friction coefficient characteristic of about 0.2 isnoted.

In FIG. 5 is shown the result of the test on the change in the frictioncoefficient of guides against the change in the relative humidity, whenthe tape used is a magnetic tape made of Co-Fe O and when the tape speedis 19 cm/s and when the temperature (room temperature) is 40 C. In FIG.5, the vertical axis represents friction coefficient p. and thehorizontal axis represents relative humidity H(percent). The Curve 17indicates the change due to the use of the electro-conductive ceramicguides of the present invention, and the Curve 18 indicates the changedue to the use of conventional metal guides. As will be understood fromFIG. 5, the guides according to the present invention show the change inthe friction coefficient p. the value of which is of the order of 0.2and show a positive characteristic, i.e., the value of p. increasessomewhat with an increase in the relative humidity. However, whencompared with the change due to the use of conventional metal guides, itmay be said that the amount of the change is very small.

Also, tests were conducted on the hardness of the electro-conductiveceramic guides of the present invention. By Vickers hardness test with atest load of 25 grams, the hardness of the guides was found to be I ,4501,600. In other words, the guides of the present invention were found tobe good in workability such as cutting and grinding.

The electro-conductive ceramic guides which are each comprised of ashaped sintered piece of TiO phase have a further advantage that theyare useful in inhibiting the static charging on the magnetic tapesbecause of the fact that although the sintered piece of TiO phase is ametal oxide porcelain, it has a very high electro-conductivity. Morespecifically, the sintered piece of TiO phase is of a highelectro-conductivity of the order of 1,000 2,000 (O cm) at room temper-5 ature due to the presence of oxygen and due to the lattice defects oftitanium. Therefore, even when there occurs a static charge on themagnetic tape for any reason, this static charge on the tape can beremoved by being led to the outside of the system through a metal membersuch as a screw 2 or a threaded rod 7 as the tape is brought intocontact with the guide A or B which is made with a highlyelectro-conductive, shaped sintered piece of TiO phase. As a result, itis possible to prevent the occurrence of an erroneous action caused bythe static charging on the magnetic tape and the occurrence of wow orflutter, at the time of recording and reproduction. Moreover, the guideminimizes the deposition of dust thereon and on the tape. Thus, theguide of the present invention has much superior functions when comparedwith those of the guide made with an electrically insulated metal oxideporcelain.

Also, the electro-conductive ceramic guide according to the presentinvention is of a good thermal conductivity. Thus, it develops a verylittle thermal shock, and does not become over-heated during use.Accordingly, it is suitable also as a guide for use in the manufacturingprocess of synthetic filaments, fibers and films. In such a case, theguide serves to prevent the development of fluff of filaments, fibersand films and to prevent their sticking or adherency due to damage orgenerated static electricity,-and thus serves to an improvement of thequality and productivity of such arti-. cles. r

Next, with respect to the manufacturing method of the electro-conductiveceramic guide, metallic titanium is first mixed with titanium dioxide(TiO at the mol ratio of 1 0.66 1.22, and the mixture is molded into anelement of the desired shape such as A or'B. This element is thensintered at a temperature of l,200- 1,450 C in vacuum or in an inertgas. Thus, the sintered element is obtained as a sintered piece of TiOphase. The resulting TiO will have a composition ratio between TiO andTiO, and the crystal particles of this element gains a face-centeredcubic structure, which is very convenient in satisfying the objects ofthe present invention. More specifically, in case the mixing proportionis such that titanium dioxide is less than 0.66 relative to 1 ofmetallic; titanium, the resulting crystal particles will have astructure which is mainly not of face-centered cubic of TiO phase, butwill be that of multi-component system containing bodycentered cubic orthe like. This latter structure is physically fragile and accordingly isno longer proper for a guide. On the contrary, if the proportion oftitanium dioxide is in excess-of 1.22 relative to l of metallictitanium, the crystal particles will have a structure which is mainingnot that of a face-centered cubic, but will be that of a multi-componentsystem containing rhombic system or the like other than the TiO phase,which is low in 'electro-conductivity and physically fragile and has alarge frictional coefficient and is no longer suitable for 'a guide.According to the present invention, sintering is performed in vacuum orin an inert gas, and the element is not' exposed to the effect of oxygencontained in the outsideatmosphere. It is, therefore, possible toobtain, accurately and easily, the desired TiO in accordance with themol ratio between the metallic titanium and the titanium oxide. Inaddition, in the manufacture of the electro-conductive ceramic guide ofthe present invention, if it is arranged so that only that portions ofthe element'which are brought into contact with the running tape or likearticle are made with such a sintered piece of TiO phase as statedabove, and that the remaining portions are made with an ordinary metalmaterial and that these two groups of portions are united to each other,it will be reasonable with respect to both the cost and themanufacturing techniques. It should be noted also that although thecomposition of the aforesaid TiO phase sintered piece is of the TiOratio between TiO and TiO the composition ratio of TiO is the mostproper for a guide.

As stated above, the electro-conductive guide of the present inventionwhich is comprised of a molded sintered piece of titanium monoxide whosecrystal particles have a facecentered cubic crystal structure is formedwith a material which is completely different from the materials of theconventional guides. The guide of the present invention is thus of avery small coefficient of friction and is capable of imparting a stablelow tension continuously for an extended period of time. Besides, thisguide is of a high electroconductivity and, accordingly, it has thefunction of removing the static charge accumulated on the running tapeor like article. Thus, the guide of the present invention can exhibit amarked effect as a guide for video tapes which require highly dense andhigh quality recorded sounds and recorded images.

1 claim:

1. An electro-conductive ceramic guide made with a molded sinteredelement of titanium monoxide having portions which are brought intocontact with a running tape or like article, said portions havingcrystal particles each consisting of a face-centered cubic crystalstructure 2. An electro-conductive ceramic guide according to claim 1,in which said portions comprises a straight body portion having an evenexternal, diameter throughout its length and a longitudinal central borefor the insertion ofa screw, and a bottom plate connected to said bodyportionand provided with a central through-hole aligned with'said bore.0

3. An electro-conductive ceramic guide according to claim 1, in whichsaid portions comprises a tapered body portion having a decreasingexternal diameter from base to top and a longitudinal central bore forthe insertion of a threaded rod, a top plate connected to the upper endof said body portion and provided with a central through-hole forthreadable engagement with said bore, and a bottom plate connected tosaid body portion and provided with athrough-hole aligned with saidbore.

2. An electro-conductive ceramic guide according to claim 1, in whichsaid portions comprises a straight body portion having an even externaldiameter throughout its length and a longitudinal central bore for theinsertion of a screw, and a bottom plate connected to said body portionand provided with a central through-hole aligned with said bore.
 3. Anelectro-conductive ceramic guide according to claim 1, in which saidportions comprises a tapered body portion having a decreasing externaldiameter from base to top and a longitudinal central bore for theinsertion of a threaded rod, a top plate connected to the upper end ofsaid body portion and provided with a central through-hole forthreadable engagement with said bore, and a bottom plate connected tosaid body portion and provided with a through-hole aligned with saidbore.